Dunbar’s number

The spring 2010 RSA Journal (UK) has an article by Robin Dunbar, professor of evolutionary anthropology at the University of Oxford. He has a theory that

Among primates in general, there is a simple relationship between a species' typical social group size and the size of its neocortex (very roughly, the thinking part of the brain). Humans fit nicely on to the end of this line, with a predicted group size based on our neocortex size of about 150 – the figure that is now known as 'Dunbar's number'.

He goes on to note:

That said, the 150 people in your social world do not form a homogenous group. Our research has revealed that social networks actually consist of a series of layers, or circles of acquaintanceship. The size of these layers tends to increase by a multiple of three – an inner layer of five intimates, then 15 good friends, 50 friends and 150 acquaintances, with each successive layer including those below it. As you go up through the layers, the average emotional intensity of the relationship declines, as does the frequency with which you see individuals. What seems to set the limit at 150 – the outer layer – is that you run out of time and psychological capital to give to more people.

This is a very attractive theory and could hold implications for the ways organizations are designed. In fact, as Dunbar points out, military units are often that number of people. If right, his thinking could mean that business units function optimally in groups of 150 people 'with an inner layer of five intimates' (perhaps a proxy for the units leadership team?). But in this article Dunbar does not mention hierarchies or layers and spans, although he does remark that:

In small-scale societies, the fact that the community is spatially and socially integrated means that its members can maintain social cohesion and social discipline. This doesn't mean to say that they never fall out or quarrel, but it does mean that they will look out for one another. Peer pressure is usually sufficient to police everyone's behaviour and prevent individuals from stepping too far out of line. What bonds the community together is a common sense of obligation, reciprocity and trust.

These are characteristics that any organization is constantly tyring to develop and so begs the question of whether business organizations are more successful if they are modeled to develop stable social communities, or whether things like succession planning, planned assignments in different locations, encouraging a certain amount of employee turnover, etc result in more successful organizations.

Later in the Journal there's an article The Many and the Few by Sanjeev Goyal, professor of economics at the University of Cambridge. He points out that

In a series of pioneering studies in the 1950s, Elihu Katz and Paul Lazersfeld identified a key feature of social communication: the fact that a very small fraction – about 20% – of the population, which consisted of so-called 'opinion leaders', served as the primary source of information for the rest. In the intervening decades, a number of studies on information and communication have confirmed that this is a robust feature of our social networks; we rely on a relatively small subset of our social group for information. Malcolm Gladwell calls this the 'law of the few'.

What follows is a rather clever example of how the 'opinion leaders' can influence the way people regard two technologies – one old and proven, and one new and unproven. Goyal has found that

Opinion leaders observe only a few others, while almost everyone observes them. This leads to the mass adoption of ideas and technologies whose desirability is contradicted by large amounts of locally collected information. Moreover, due to the broad adoption of such actions, the generation of information about alternatives is seriously inhibited, so the lack of experimentation can persist for a long time. …

… These findings may be interpreted in the light of Mark Granovetter's celebrated 'strength of weak ties' hypothesis. Granovetter visualises society as comprising groups of individuals who have many internal links but only a few cross-group links. Our research suggests that strong ties within groups sustain experimentation, while weak, cross-group ties carry valuable information across a broader network, thereby sustaining technological dynamism in a society.

Taken together the two articles suggest that designing workgroup communities of around 150 people with ties to influence leaders in other communities might make for a successful organization. But of course we don't know that this would happen (although Gore is an example of a successful organization which does, in fact, follow more or less those principles).

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